Conventionally, read and write commands to disk are performed immediately upon issuance of the command. Read commands generally must be performed immediately to assure smooth operation of a program. However, write commands, which occur when modified data is to be rewritten to disk, need not necessarily be performed immediately. Nevertheless, such writes to disk have been conventionally performed on an "as occur" basis. As a result, a number of head/arm movements over the disk surface occur which require substantial travel to accomplish the various write commands.
By their nature, such extended head/arm traversals over the disk surface consume time, during which, the disk is rendered unable to respond to a read command. When this occurs, program execution waits until the requested data is read.
In this invention a temporary file is provided for the storage of modified data and further provides a buffering arrangement for data which is to be rewritten to disk. Because the modified data is stored in the temporary file, there is no immediate need to rewrite it to its final position on disk. Thus the accepted procedure of writing on an "as occur" basis is unnecessary.
As the temporary file is employed during substantially every "write" operation, it is desireable to station the disk drive's read/write head directly over the track (or tracks) in which the temporary file is stored. Furthermore, the temporary file track is generally placed midway between the innermost an outermost disk tracks so that head movements to other tracks can be minimized.
Accordingly, it is an object of this invention to provide a disk drive system wherein the head/arm structure is positioned over an often-used track and head/arm write excursions are minimized.
It is another object of this invention to provide a method for minimizing head/arm excursions by performing a plurality of write actions in a single head/arm excursion.